Process for forming dialkylamino ketones and nu-alkyl-lactams



United States Patent 3,143,547 PROCESS FOR FORMING DIALKYLAMINO KETONES AND N-ALKYL-LACTAMS Philip A. Cruickshank and John C. Sheehan, Lexington,

Mass., assignors to Research Institute for Medicine and Chemistry, Inc., Cambridge, Mass., a corporation of Massachusetts N0 Drawing. Filed Mar. 27, 1961, Ser. No. 98,306

8 Claims. (Cl. 260-247.7)

This invention relates to a process for the formation of dialkylamino ketones and N-alkyl lactams. In particular, it relates to the formation of such ketones and lactams where the starting material is a gamma or delta dialkylamino acid wherein there is at least one hydrogen on the alpha carbon atom.

Prior to the present invention, synthesis of delta dialkylamino ketones has been reported as taking place by the condensation of delta bromo ketones and dialkylamines. Gamma dialkylamino ketones have been synthesized in the past by condensation of alpha halo-dialkylamino alkanes with beta ketoesters. This class of compounds, namely, the gamma and delta dialkylamino ketones are useful as intermediates in the synthesis of anti-malarial drugs. However, such previously reported processes for making such compounds usually involve starting materials that are difiicult to obtain or a reaction that is diflicult to manipulate.

N-alkyl lactams which are useful as intermediates in the preparation of polyamides have been prepared in the past by heating of the acid chlorides of gamma and delta dialkylamino acids. However, it is generally required that a temperature of 160 C. or higher be used.

In accordance with the present invention a novel process is presented for the preparation of certain gamma and delta dialkylamino ketones and N-alkyl lactams which ofiers the advantages of easily obtainable starting material, an easily manipulated reaction and a relatively moderate temperature.

This invention in its general sense comprises as a starting material a dialkylamino carboxylic acid, wherein for ketone formation at least one alkyl group is primary, and wherein there are either three or four methylene groups between the nitrogen and the carboxylic acid group. This starting material is heated with a carboxylic acid anhydride (preferably in excess) to produce the dialkylamino ketone, carbon dioxide and the carboxylic acid. Where the carboxylic acid anhydride is too high boiling a diluent such as xylene is added. The excess anhydride and diluent are preferably removed by exhaustive distillation at atmospheric pressure while the products themselves are recovered by distillation under reduced pressure. To form the lactam at least one of the alkyl substituents must be non-primary, the reaction conditions being the same as for forming the ketone.

The resultant products of this invention are not obvious from the prior art. Where the alkyl groups were secondary alkyl or benzyl substituents then pyrrolidones piperidones and secondary alkyl or benzyl esters were formed. However, when at least one of the alkyl substituents on the nitrogen was a primary alkyl group, a dialkylamino ketone was formed by incorporation of an acyl group from the anhydride and loss of carbon dioxide.

The primary alkyl substituents which can be placed on the nitrogen atom include not only pure alkyl groups but also those which have, in the beta or subsequent carbon atoms, aromatic substituents or any other substituent non-reactive to the anhydride, provided that the alpha methylene group in the alkyl is unsubstituted. Also, cyclic groupings may be used, e.g., morpholine and piperidine. If both of the alkyl substituents on the nitrogen are primary a high yield of ketone results. If one aLryl is primary but the other alkyl is not, both lactarn and ketone will be formed with a predominance of lactam. Where both alkyls are non-primary, lactam is formed but no ketone.

As specific examples of this invention, gamma dialkyl aminobutyric acid, delta dialkylamino valeric acid and gamma dialkylamino valeric acid were prepared and then heated under reflux with an excess of either acetic anhydride or propionic anhydride-xylene mixture. In the case of gamma dialkylamino butyric acid the alkyl pairs included two primarys, one primary and one secondary, and two secondarys. The resultant ketones were identified by their semi-carbazones and in one case by methiodide.

The dialkylamino acid is preferably prepared by first forming the ester, hydrolyzing with strong hydrochloric acid or KOH to form the acid hydrochloride or salt and then neutralizing to form the free acid. The preferred method of forming the ester is to react the secondary amine with the iodester.

Table I illustrates the dialkylamino esters formed from a solution of the methyl gamma iodo-butyrate by heating with four equivalents of the appropriate secondary amine in benzene at 60 C. for three hours. After cooling the amine hydrochoride is removed as a precipitate and the product recovered from the filtrate by concentration and distillation under reduced pressure.

Table II illustrates the acid hydrochlorides formed from the esters shown in Table I. A solution of the ester in 18% aqueous hydrochloric acid is heated under reflux for 6 to 8 hours. The solution is then dried under reduced pressure and solid residue crystallized from a suitable solvent.

The aqueous solution of the hydrochloride is adjusted to pH 7 with aqueous sodium hydroxide to form the acid. After removal of the water under reduced pressure the dry residue is extracted with several portions of hot chloroform. These extracts are then evaporated under reduced pressure and the residues of crude acid used without purification.

In the valeric acid series the delta dialkylamino valeric acid is prepared by reacting in absolute ethanol the corresponding amino propyl chloride with ethyl malonate in the presence of sodium and then heating with 18% aqueous hydrochloric acid under reflux to simultaneously hydrolyze and decarboxylate.

In another method, methyl gamma chlorovalerate is converted to the iodo-valerate and then refluxed with amine to form the methyl ester which in turn is hydrolyzed to form the free acid.

In one case, methyl gamma-chlorovalerate was prepared from gamma-valerolactone with anhydrous hydrogen chloride in methanol, and then converted to the methyl gamma-iodovalerate by means of sodium iodide in acetone. A solution of the iodovalerate in benzene was refluxed with four equivalents of morpholine to yield the gamma-(4-morpholine) valerate which was acid hydrolyzed to give the hydrochloride.

In carrying out the reaction of this invention the di-' alkylamino acid is first dissolved in an anhydride, as for example, one part of acid by weight to 4 parts of acetic anhydride by volume, and then heated under reflux for 15 minutes under an atmosphere of purified nitrogen. Any resultant gases are passed through barium hydroxide solution where the appearance of a precipitate indicates formation of the ketone. Distillation at atmospheric pressure is carried out until the temperature reached to 200 C. This removes the excess anhydride, as well as solvent or diluent. By further distillation under reduced pressure the ketones and lactams of this invention are recovered.

Table III summarizes the properties of the ketones and lactams formed from the carboxylic acids corresponding to the hydrochlorides of Table II. In Table HI the prod- 4 137 C. after recrystallization from methylene chloridepetroleum ether.

(C H N O Calc.: C, 54, 52; H, 9.15; N, 23.13. Found: C, 54.99; H, 9.39; N, 22.50.

5 A methiodide of 5-(1-piper-idiiio) -2-pentanone was prepared by refluxing a solution of the ketone in acetone and methyl iodide for 2 hours. After recrystallization from acetone ether the derivative had a melting point of 70' (C H NOI) Cale; C, 42.45; H, 7.13; N, 4.50; I, 40.78. Found: C, 42.61; H, 6.93; N, 4.52; I, 40.90.

Table I Methyl 1 Dialkylaminobutyrates N (0 H2) -C 0 C H3 R Carbon, Hydrogen, Nitrogen, Yield, Empirical percent percent percent N- percent B. P. 'n,.( C.) formula R Calcd Found Calcd. Found Calcd. Found Piperidino 98 1. 4578(24) CroHmNOg. 10. 29 7. 56 7. 80 Morph0lino. 95 1. 4582 (22) CQHHNOL- 9. 21 7. 48 7. 67 N-metliylbenzy 82 1. 0568 (22) CiaHisNOz. 8. 66 6. 33 6. 58 Dibenzyl amino 76 1. 5436() CIQGZSNOZ- 7. 66 4. 71 5. 24 Dicyclohexylamino 82 C17H3 NO 10. 4. 98 4. 96 Diethylarnino- 92 1. 4392 (26) Di-n-propylamino 88 1. 4348(24) C11H23N02 6. 96 6.90 Di-isopropylamin 76 6670/1 mm 1. 4385 (24) CnHmiNOz 6. 96 6. 54

* Toluene heated under reflux as reaction medium. b M.P. 5556.5; recrystallized from acetone-water.

Table II 7 (b) -D ialkylamino Acid Hydro chlorides N (CH;) n-C OzH-HCI R Carbon, Hydrogen, Nitrogen, Chlorine, I Yield, Crystal- Empirical percent percent percent percent 1 n percent M.P., lization formula. solvent B R Calcd. Found Calcd. Found Calcd. Found Calcd. Found Pipei'idino- 3 94 190-2 A C sHraClN O2. 52. 04 51. 89 8. 73 8. 73 6. 75 6. 71 17 07 17. 64 Morpholino 3 95 180-2. 5 A CsHmClN O2. 45. 82 45. 92 7. 69 7. 6. 68 6. 82 N-l\.[ethylbenzylamin 3 89 172. 5-4. 5 A O12H1EOINO2 59. 13 59. 41 7. 44 7. 59 5. 6. 04 14. 55 15. 12 Dibenzylarnino 3 b 90 135. 5-6. 5 B ClBH22ClNO2 67. 59 67.36 6. 93 6. 74 4. 38 4. 49 11.09 10.97 Diethylarm'no- 3 83 167-70 C CsHigClNO 49. 10 49. 38 9. 27 9. 13 7. 16 7. 38 Di-n-propylamjno. 3 88 119-21 C C1uHi C1NO 53. 68 53. 65 9. 91 9. 64 6. 26 6. 14 15. 15.72 Di-isopropylamino- 3 77 141. 5-4 C C oHz2ClNOz 53. 58 53. 57 9. 91 9. 75 6. 26 6. 40 15. 85 15. 63 D imethylamino 4 97 163-5 C C 1H1aClN 0L 46. 28 46. 66 8. 88 9. 06 7. 71 7. 68 19. 52 19. 37

' A-acetic acid/acetone; Bacetic acid; Cacetic acid/ether. b Prepared from free acid; latter obtained by saponification of methyl ester.

Table III H 1| /N(CH2)n-CO2H+(R CO)iO /N(CHz) -CR"+( Hm "-C O2R+CO3 R R N R A B C A R Carbon, Hydrogen, Nitrogen, Yield, Empirical percent percent percent /N n R" Product percent B.P., /m m. n,,( C.) formula V I R Calcd. Found Calcd. Found Calcd. Found Piperidino- 3 CH3 A 58 97/7 1. 4628(23) 11. 31 11. 22 8. 28 8. 34 Morph0lino- 3 CH3 A 58 81/0. 5 1. 4630(24) 10. 01 9. 82 8. 18 8. 16v Morpholino 3 CzH5 A 57 92/0. 75 1. 4627(25) 10. 34 10. 36 7. 56 7. 75 N -1nethylbenzyl- 3 CH3 2% 12 119-22/1. 2 1 5009 (23) 6. 82 6. 99 67 o a 57 Dibenzylamino 3 CH3 g 2 71 7 48 7 50 8. 00 7 0 Dicyclohexylamino 3 CH3 B 85 1. 4985 (24) 10 25 10.02 8 38 8. 84 Diethylamlno 3 CH3 A d 47 -3/760 1. 4462 (24) 81 9. 77 5 05 5. 35 D propylamino 3 CH3 A d 64 98/9 1. 4369 (24) a D isopropylainlno 3 CH3 B e 66 82. 5/7 1. 4581 (26) 10. 30 10. 19 O2 10; 76 Dnnethylammo- 4 CH; A d 42 85-8/11 1. 4474 (22) vi B1 methylpyrrolidone; C benzyl acetate; compounds could not be separated by distillation. Countercurrent distribution between water'and ether gave pure substances, identified by refractive index and infrared spectrum.

b Bbenzylpyrrolidone; C-benzyl acetate.

0 Bcyclohexylpryrolidone; co-produot (cyclohexylacetate) Was not isolated.

d Distilled with two moles of acetic acid. Mixtures converted directly e Bisopropylpyr'rolidone; copr'oduc't (isopropyl'acetate) was not isolated to semicarbazone derivatives.

Table IV R NNH-CO-NH2 H Semlcarbazone Derivatives Hz) DCR" R Carbon, Hydrogen, Nitrogen, I Empirical percent percent percent /1 n R" M .P., Crystallization solvent formula R Calcd. Found Caled. Found Calcd. Found Piperidino- 3 CH; 132-3 Benzene-pet. ether C11HHN4O 58.37 58.43 9.80 9.66 24.76 25.00 Morpholino- 3 CH3 145-6 Tetrahydroiuran-pet. ethezz- C1uH:oN40z 52. 61 52.94 8.83 9.02 24. 54 24. 79 Morpholino 3 C211; 146-7 Methylene chloride-ether C11H22N40g 54.52 54.24 9.15 9.12 23.12 23.09 N -methylbenzyl 3 CH3 105-7 Acetone C14HzzN4O 64.09 64.20 8. 45 8.64 21.36 21. 52 Diethylamin0- -1 3 CH3 93. -4.5 Ether-pet. ether.- CroHzz 4 56.04 56.07 10.35 10.09 26. 14 26. 00 Dim-propylamino 3 CH3 84-55 Pet. ether C12HmN4O 59.47 59.58 10.81 10.42 23. 12 22.74 Dimethylamino- 4 CH3 95-7 Methylene chloride-pet. ether CuHzuN 53.97 54.29 10.07 10.18 27.97 28.19

We claim: said ketone being a member of the group consisting of 1. A process for forming dialkylamino ketones and N-alkyl-lactams, comprising heating a dialkylamino acid with an excess of a member of the group consisting of acetic anhydride and propionic anhydride in a nitrogen atmosphere; said acid being a member of the group consisting of:

R'\ CH3 NH(CHz) 2-0 0 OH RI! and N-(CH ,.-G 0 0E RI! wherein n=3 to 4; R, R" being non-tertiary alkyl having one to seven carbon atoms,

dialkylamino ketone being formed if R and R are both primary alkyl, N-alkyl-lactam being formed if R and R are both secondary alkyl, and a mixture of ketone and lactam being formed if R is primary alkyl and R" is secondary alkyl.

2. The process of claim 1 wherein R and R" are selected from the group consisting of methyl, ethyl, propyl, isopropyl, benzyl, methylbenzyl, cyclohexyl, morpholino and piperidino.

3. A process for forming a mixture of dialkylamino ketone and a N-alkyl lactam, comprising the process of claim 1 wherein R is a primary and R" is a secondary alkyl.

4. The process of claim 3 wherein R is benzyl.

5. A process for forming a dialkylamino ketone, comprising heating a dialkylamino acid with an excess of a member of the group consisting of acetic anhydride and propionic anhydride in a nitrogen atmosphere; said acid being a member of the group consisting of wherein 11:3 to 4, X, X" being primary alkyl having one to seven carbon atoms,

wherein n, X, X" are as above and R is selected from the group consisting of CH and C H 6. The process of claim 5 wherein X and X are selected from the group consisting of methyl, ethyl, propyl, morpholino and piperidino.

7. A process for forming an N-alkyl lactam comprising heating a dialkylamino acid with an excess of a member of the group consisting of acetic anhydride and propionic anhydride in a nitrogen atmosphere; said acid being a member of the group consisting of wherein Z, n are as above.

8. The process of claim 7 wherein Z and Z are benzyl.

References Cited in the file of this patent Morton: The Chemistry of Heterocyclic Compounds, p. VI of the preface, N.Y., McGraw-Hill, 1946. 

1. A PROCESS FOR FORMING DIALKYLAMINO KETONES AND N-ALKYL-LACTAMS, COMPRISING HEATING A DIALKYLAMINO ACID WITH AN EXCESS OF A MEMBER OF THE GROUP CONSISTING OF ACETIC ANHYDRIDE AND PROPIONIC ANHYDRIDE IN A NITROGEN ATMOSPHERE; SAID ACID BEING A MEMBER OF THE GROUP CONSISTING OF; 